Injectables basically fall into two categories:
(1) Hyaluronic acid based fillers such as Juvederm, Restylane, etc which are temporary and leave no trace behind once they are reabsorbed
(2) Microsphere based fillers such as Radiance (Radiesse) or Artefill which are semi-permanent to permanent and often leave traces behind after the substance has been reabsorbed
There are other injectables which fall under a different category (such as silicone) but for now the above two categories are the main ones uses in the United States and are FDA approved.
Restylane, Juvederm are injected into the dermis below the wrinkle to lift it out to the desired correction. For lip augmentation they are injected directly into and around the lips. These substances integrate into the dermis and simply binds with water. They do nothing to interfere with metabolism or oxygen absorption. Eventually these substances are completely reabsorbed after 6 to 12 months. These a very safe filler since even if they aren't injected properly generally speaking there shouldn't be any long term side effects assuming a nerve or some other vital structure was damaged during the injection - I've never heard of this happening.
Artefill which is made out of microscopic spheres must be injected within the deep dermis or subdermis layers to prevent clustering of the spheres and also due to the substance not being as soft as the hyaluronic acid based fillers. Radiesse is similar to this with the exception that it's not permanent as Artefill claims to be. Radiesse uses microspheres composed of calcium which is a harder substance too, so you can imagine why it is not a good idea to inject this into softer areas such as the lips.
From my experience, Radiesse does not last long enough to warrant the price tag which is nearly twice as much as Juvederm Ultra Plus (which last 7 to 9 months). Radiesse only lasts 8 to 12 months and can have semi-permanent side effects such as clumping so at this point in time I'd advise sticking with the hyaluronic acid based fillers (Restylane/Perlane, Juvederm/Juvederm Ultra Plus, etc) until something longer lasting without side effects comes along.
“One popular new plastic surgery technique is called lip grafting, or "fat recycling" wherein fat cells are removed from one part of your body that is too large, such as your buttocks, and injected into your lips; people will then be literally kissing ass.”